The present invention relates generally to the therapeutic use of laser radiation, and more particularly to the interstitial application of laser radiation therapy to tissue masses.
Non-contact treatment of malignant tumors by laser irradiation, predominantly using Nd;YAG lasers, has been practiced for more than a decade, and significant numbers of reports concerning its effectiveness as a procedure exist. Patients having advanced esophageal, bronchial, colorectal and bladder tumors, have been successfully pallidated using this technique. Researchers have also tested the possibility of treating more deeply located tumors by inserting the laser probe, either alone or through a needle, into the lesion. This interstitial method of coagulation by hyperthermia with subsequent coagulative necrosis, however, has been hampered by damage to the tip of the fiberoptic probe with consequent loss of laser energy transmission. The damage has been found to be the consequence of adhesion of the heated tissue to the quartz fiber with resulting charring thereof, and the subsequent absorption of intense laser energy at the interface. Defacing of the fiber tip has been observed. This problem has been partially overcome by: a. reducing the laser output power from the 20-40 Watt range to 0.5-2.0 Watts while simultaneously increasing the irradiation exposure time; b. coating the probe tip with sapphire which has a higher melting point than quartz and also diffuses the light; or c. inserting the fiber into a plastic sheath with circulating coolant fluid within the sheath around the fiber tip.
The article entitled "Nd:YAG Laser-Induced Interstitial Hypethermia Using A Long Frosted Contact Probe," by Masoud Panjehpour et al., published in Lasers In Surgery And Medicine 10, 16 (1990), identifies the need to apply laser radiation interstitially rather than to the surface of a tumor in hyperthermic treatment of any sizable tissue masses. The authors describe a frosted contact probe utilized to diffuse the laser light over the entire area of the frosted length, thereby reducing the power density at the tip while providing sufficient heating. Insignificant histological changes are reported from treatments at power levels as high as 4 Watts. However, at a 5 Watt power level, after 30 mn. of irradiation, some level of necrosis occurred.
In U.S. Pat. No. 4,669,465, for "Laser Catheter Control And Correcting Apparatus" issued to Gary L. Moore et al. on Jun. 2, 1987, the investors teach an angioplasty catheter apparatus for delivering laser light to obstructions in blood vessels. A light transmitting optical fiber is inserted into an elastic tube through which saline solution is passed coaxially with the fiber and out the end thereof from which the laser light is emitted. The saline solution is infused continuously during the laser operation with the initiation of the infusion being shortly prior to the irradiation process in order to provide greater fluid clarity during the irradiation, to provide a better medium for the laser energy at the site, and to carry away debris formed as a result of the procedure, thereby keeping the laser fiber tip and the zone immediately adjacent thereto substantially free of such debris. Moreover, the inventors teach that during the laser operation, the fiber tip is advanced through the substance to be removed, and that irradiation must not occur while the tip of the lasing fiber is retracted within the catheter. The elastic catheter is tipped with an inflatable balloon, rendering the entire apparatus suitable only for insertion into orifices and vessels.
In the articles entitled "Tumor Therapy With Hematoporphyrin Derivative And Lasers Via A Percutaneous Fiberoptic Technique: Preclinical Experiments, by R. A. Gatenby, N. D. Hammond, and D. Q. Brown, Radiology 163, 163 (1987), and "CT Guided Laser Therapy In Resistant Human Tumors: Phase I Clinical Trial," by R. A. Gatenby et al., Radiology 163, 172 (1987), the authors teach the insertion of a 400 micron diameter optical fiber having a terminal cylindrical diffuser into a flexible teflon sheath catheter which is then inserted into tumors. The tissue to be treated is first sensitized using a hematoporphyrin derivative, and a maximum power of 1.2 Watts from an argon ion laser-pumped dye laser emitting wavelengths greater than 600 nm is employed to photolyze the hematoporphyrin thereby producing chemically active species which interact with the tissue mass. An average of 900 Joules of energy were applied resulting in a mean temperature rise in the tumor of 9.degree. C. Therefore, there was some response of the tumor to hyperthermia, although the authors report that the principal effect was chemical. No blood clot adherence to the optical fiber with consequential charring was observed, presumably as a result of the low output power and the diffuse nature of the laser light.
In "In Depth Radiation Therapy by YAG Laser For Malignant Tumors In The Liver Under Ultrasonic Imaging," by D. Hashimoto, M. Takami, and Y. Idezuki, Gastroenterology 88, 1663 (1985), the authors describe precise localization and needle diagnosis of lesions deeply located in various organs using radiographic, sonographic and computerized tomographic techniques. However, there is no teaching of the use of such needles as part of the laser therapy procedure.
Accordingly, it is an object of the present invention to provide an apparatus and method for treatment of solid tumors located in various organs by laser-induced hyperthermia with subsequent coagulative necrosis without the usual concern that laser energy transmission to the target tissue mass would degrade as the procedure is continued.
Another object of our invention is to provide an apparatus and method for efficient and rapid treatment of solid tumors located in various organs by laser-induced hyperthermia with subsequent coagulative necrosis.
Yet another object of the present invention is to provide an apparatus and method for treatment of solid tumors located in various organs by laser-induced hyperthermia with subsequent coagulative necrosis while inducing a minimum of damage to surrounding, healthy tissue.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.